【作者】 李毅；

【导师】 喻万景；

【作者基本信息】 中南大学 ， 材料冶金， 2024， 硕士

【摘要】 近年来,新能源产业的迅速发展促进了锂离子电池需求的快速提升,这也导致了锂离子电池报废数量的持续增长,废旧锂离子电池的回收利用变得十分必要且急迫。针对目前锂离子电池三元正极材料回收流程提锂效率低、工艺流程长等问题,本文以废旧镍钴锰酸锂三元正极材料为研究对象开发了优先提锂-水热再生工艺实现废旧三元正极材料的高效回收与再生,并同步实现了废旧三元正极材料的共晶锂盐短流程再生,具体研究内容如下:开发了氯化铵体系富氧气氛焙烧-水浸提锂工艺,选择固体氯化剂NH₄Cl氯化正极材料形成金属氯化物,并在焙烧过程中利用金属氯化物的稳定性不同而选择性氧化过渡金属,随后进行水浸提锂并制备碳酸锂。在焙烧温度为600°C,氯化铵摩尔量为废旧正极材料中Li摩尔量的2倍,焙烧时间为60 min的最佳条件下,Li、Ni、Co、Mn的浸出率分别为97.81%、0.66%、1.05%、0.05%,由浸出液沉淀制备的碳酸锂纯度高达99.40%。提锂渣经还原酸浸后调整浸出液pH值与过渡金属离子浓度,采用水热法合成NCM811高镍三元正极前驱体并烧结制备正极材料。未除杂浸出液合成的正极材料具有较高的容量保持率,在水热温度为170°C,水热时间为12 h,聚乙二醇为10 wt.%时,合成的材料1C下首次放电比容量为164.41 m Ah·g^-1,200圈容量保持率为83.30%。采用共晶锂盐策略再生混合废旧三元正极材料,结果表明相较于高温固相再生,该策略能明显提升材料的放电比容量与倍率性能。Li OH-Li₂CO₃共晶锂盐体系再生的材料具有最佳的电化学性能,1 C首圈放电比容量为146.39 m Ah·g^-1,100圈容量保持率96.17%,10 C大电流密度下放电比容量达到131.7 m Ah·g^-1。图56幅,表20个,参考文献128篇更多还原

【Abstract】 In recent years,the rapid development of new energy industry has promoted the rapid increase in the demand for lithium-ion batteries,which has also led to a sustained increase in the number of end-of-life lithium-ion batteries.The recycling and utilization of spent lithium-ion batteries has become necessary and urgent.In response to the current problems of low lithium extraction efficiency and long process flow in the recycling of ternary cathode materials for lithium-ion batteries,this thesis presented a priority lithium extraction-hydrothermal regeneration process for spent lithium nickel cobalt manganese oxide ternary cathode materials.The objective is to achieve efficient recycling and regeneration of spent ternary cathode materials.Additionally,the short flow regeneration process of eutectic lithium salt of spent ternary cathode materials was synchronously realized.The specific research contents are as follows:A novel ammonium chloride system oxygen-enriched roasting and water leaching process was developed.Solid chlorinating agent NH₄Cl was selected to chlorinate the cathode materials to form metal chlorides.The stability of the metal chloride was exploited to selectively oxidize the transition metal during the roasting process.Subsequently,lithium was extracted by water leaching and lithium carbonate was prepared.Under the optimal conditions of roasting temperature of 600°C,ammonium chloride dosage twice the molar amount of Li in spent cathode material,and the roasting time of 60 minutes.Under these conditions,the leaching rates of Li,Ni,Co,and Mn are 97.81%,0.66%,1.05%,and 0.05%,respectively.The purity of lithium carbonate prepared by precipitation from the leachate was as high as 99.40%.Following the reduction and acid leaching of the lithium extraction residue,the p H and transition metal ion concentration of the leach solution were adjusted.The NCM811 high-nickel ternary cathode precursor was synthesized by hydrothermal method and sintered to prepare cathode materials.The cathode material synthesized using untreated by impurity removal leachate has a higher capacity retention rate.At a hydrothermal temperature of 170°C,a hydrothermal time of 12h,and a polyethylene glycol addition of 10 wt.%,the synthesized cathode material exhibited a first discharge capacity of 164.41 m Ah·g^-1 at 1 C,and a capacity retention rate of 83.30%after 200 cycles.The eutectic lithium salt strategy was employed to regenerate the mixed spent ternary cathode materials.The results demonstrated that compared to high-temperature solid-state regeneration,this strategy could significantly improve the discharge specific capacity and rate performance of the materials.The regenerated material of the Li OH-Li₂CO₃ eutectic lithium salt system exhibited a first discharge capacity of146.39 m Ah·g^-1 at 1 C,and a capacity retention rate of 96.17%after 100cycles.The discharge capacity reached 131.7 m Ah·g^-1 at a high current density of 10 C.更多还原